The Muscle Tissue/Cell Culture/Diagnostics Core for this Wellstone Muscular Dystrophy Cooperative Research Center is a multifaceted laboratory that serves as a local and a national resource for muscular dystrophy research. There are two major goals of the Core. First, the Core will maintain and continue to grow the Repository of skeletal muscle biopsies and cell cultures established during the first five years of funding. Among the existing muscle biopsies are more than 1000 muscular dystrophy samples that include dystrophinopathies (Duchenne and Becker muscular dystrophy), limb-girdle muscular dystrophies, and congenital muscular dystrophies. More than 125 patients (primarily muscular dystrophy patients) have undergone skin biopsies to establish fibroblast cultures in the Repository. We will accrue new specimens into the Repository from a variety of sources: diagnostic muscle biopsies, therapeutic surgical procedures, endomyocardial biopsies, heart explants, skin biopsies, and autopsies. Patients with genetically defined muscular dystrophies are recruited to undergo biopsies in order to maintain a widely representative spectrum of muscular dystrophy diagnoses. Well-characterized tissues and cells from the Core are made available to research investigators at lowa and other academic centers. The second goal of the Core is to provide specialty diagnostic resources unavailable in clinical laboratories. This includes western blots from skeletal muscle as well as on-cell westerns and nuclear morphology assays in cultured cells. The Core facilitates development of new diagnostic tests for transfer to the clinical laboratory, and serves as a post-intervention biopsy evaluation resource for investigators conducting clinical trials. Thus, the Muscle Tissue/Cell Culture/Diagnostics Core maintains a vital resource of muscular dystrophy tissues and cell cultures, provides a critical diagnostic link in expanding the number of patients with specific, molecular diagnoses, and serves as a national biopsy testing resource for clinical trials in muscular dystrophy patients.